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| class Solution {
public String shortestPalindrome(String s) {
if (s.length() <= 1) {
return s;
}
if (s.length() % 2 == 0) {
int startIndex = s.length() / 2 - 1;
while (startIndex >= 0) {
int i = startIndex, j = startIndex + 1;
while (i >= 0) {
if (s.charAt(i) == s.charAt(j)) {
i--;
j++;
} else {
break;
}
}
if (i == -1) {
return appendToString(s, j);
}
i = startIndex;
j = startIndex;
while (i >= 0) {
if (s.charAt(i) == s.charAt(j)) {
i--;
j++;
} else {
break;
}
}
if (i == -1) {
return appendToString(s, j);
}
startIndex--;
}
} else {
int startIndex = s.length() / 2;
while (startIndex >= 0) {
int i = startIndex, j = startIndex;
while (i >= 0) {
if (s.charAt(i) == s.charAt(j)) {
i--;
j++;
} else {
break;
}
}
if (i == -1) {
return appendToString(s, j);
}
i = startIndex - 1;
j = startIndex;
while (i >= 0) {
if (s.charAt(i) == s.charAt(j)) {
i--;
j++;
} else {
break;
}
}
if (i == -1) {
return appendToString(s, j);
}
startIndex--;
}
}
return "";
}
private String appendToString(String s, int j) {
StringBuilder sb = new StringBuilder();
while (j < s.length()) {
sb.append(s.charAt(j));
j++;
}
return sb.reverse().append(s).toString();
}
}
|